The present invention relates generally to distributed communication systems, in particular, telephony-over-local area network (LAN) (ToL) communication systems, and the like, and more specifically, to an apparatus and method for providing an alternative or secondary voice messaging system for a distributed communication network.
Distributed communication systems such as telephony-over-LAN (ToL) communication systems and the like are highly complex networked systems containing a plurality of elements or devices for routing calls to users of the system. For example, an exemplary ToL system might include a network having two or more sub-networks, each sub-network including a plurality of clients providing communication services to multiple users. Such a ToL system may further include one or more gatekeepers for assisting in the routing of calls to destinations within the system, a gateway for interconnecting the ToL system with an external switched circuit network such as the public switched telephone network (PSTN) or a private branch exchange (PBX), a multipoint control unit (MCU) providing support for conferences of three or more clients, a messaging server, a feature server, and the like.
When an event such as a power failure, a network or sub-network outage, or a site closure due to weather or disaster renders elements of a ToL system inoperative, it is desirable to divert calls received during the event to a messaging server, voicemail server, or the like so that the call may be answered. However, because of the complexity of typical ToL systems, forwarding of calls to messaging systems within a ToL system may involve many steps. For example, a call from an external caller may first go through a gateway. The gateway may then consult a gatekeeper and be routed to a client of the ToL system such as an IP (Internet Protocol) telephone, personal computer soft client, or the like. If the client provides no response, the call may be forwarded to a messaging system where a voicemail message may be left for the user. Further, some ToL systems may employ a messaging system using native IP or other protocols to link with the ToL system. Moreover, some ToL systems may have only one domain while other ToL systems may have many. As a result, during an outage of the ToL system caused by power failure, network or equipment failure, or the like, it is likely that an external caller may be unable to leave a message on the messaging system employed by the ToL system, because the gateway cannot reach through the broken network to reach the messaging system and would instead experience fast busy or ring-no-answer tones.
Consequently, it is desirable to provide a communication system having an external or secondary messaging system that is coupled to the ToL system for providing a temporary storage cache where messages may be left when elements of the ToL system cannot be reached due to outage events.